3

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Why do industrial seed oils have high smoke point?

Answered on August 19, 2014
Created July 01, 2012 at 12:45 AM

Industrial seed oils are high in PUFA. If PUFA is easily oxidized, how do they have high smoke points? What am I misunderstanding?

Medium avatar

(10611)

on July 03, 2012
at 05:29 AM

The problems with unsaturated fats is more related to cross linking than smoking. As you say, there's lots of high volatility stuff in unrefined oils. Generally any compound associated with flavor or aroma is more prone to smoke than the oil, and these would be stripped out in refining.

Medium avatar

(10611)

on July 03, 2012
at 05:28 AM

The problems with unsaturated fates is more related to cross linking than smoking. As you say, there's lots of high volatility stuff in unrefined oils. Generally any compound associated with flavor or aroma is more prone to smoke than the oil, and these would be stripped out in refining.

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on July 03, 2012
at 01:55 AM

am I misunderstanding? Even lard and tallow have some polyunsatured fats. Wouldn't it be apparent if they were oxidizing during frying?

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on July 03, 2012
at 01:54 AM

I am looking for the kind of table you're describing. I haven't found one yet, but it seems if you take olive oil as an example. If you use refined olive oil, the smoke point is high, and I've had french fries cooked in refined olive oil. I believe olive oil can oxidize at room temperature over a period of a year or two. Deep frying is at least 200 degree above room temp and (2 years / 2^(200/10)) is a very short time period. That means the olive oil french fries should smell or taste off, right? But they don't. I know you said 10 degrees/doubling is a rule of thumb and not linear, but...

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on July 03, 2012
at 01:52 AM

other factors, but am I misunderstanding?

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on July 03, 2012
at 01:52 AM

I am looking for the kind of table you're describing. I haven't found one yet, but it seems if you take olive oil as an example. If you use refined olive, the smoke point is high, and I've had french fries cooked in refined olive oil. I believe olive oil can oxidize at room temperature over a period of a year or two. Deep frying is at least 200 degree above room temp and (2 years / 2^(200/10)) is a very short time period. That means the olive oil french fries should smell or taste off, right? But they don't. I'm sure the 10 degrees/doubling is a rule of thumb and there are lots of...

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on July 03, 2012
at 12:56 AM

Thank you, miked. Very helpful.

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on July 01, 2012
at 06:53 PM

I don't think oil processing intentionally liberates free fatty acids.

510bdda8988ed0d4b0ec0b738b4edb73

(20898)

on July 01, 2012
at 03:06 PM

Well, we prefer the term chemist, but chemistry guy works too. Anyway, I've answered your questions as a big edit in my original answer above. It was easier that way then adding more comments here.

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on July 01, 2012
at 11:27 AM

So are there oxidation points (temps) for each type of oil? Do you know of a resource that lists them? Even tallow has some PUFA and MFA, right? So that portion of the fat would be oxidized when cooking?

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on July 01, 2012
at 10:59 AM

Oh, that makes a lot of sense. Same with how ghee has a higher smoke point than butter, right?

A2c38be4c54c91a15071f82f14cac0b3

(12682)

on July 01, 2012
at 03:36 AM

Hey chemistry guy (can I call you that?), I have heard smoke point relates to how many free fatty acids there are relative to triglycerides in the oil, is this sort of correct?

0d0842381492a41b2173a04014aae810

(4875)

on July 01, 2012
at 01:08 AM

I'd like to know a bit more about smoke points in general. How is avocado oil above 500, being mostly MUFA? Clearly the saturation of the fatty acids isn't the (only?) determining factor. Coconut smokes pretty low.

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4 Answers

best answer

5
32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on July 01, 2012
at 04:07 AM

It's not the triglycerides that are necessarily unstable. It's whatever else is in the oil. Take olive oil as an example. The smoke point increases as you further refine it. You're removing the other things, such as phytochemicals, that are very easily oxidized/burned.

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on July 01, 2012
at 10:59 AM

Oh, that makes a lot of sense. Same with how ghee has a higher smoke point than butter, right?

Medium avatar

(10611)

on July 03, 2012
at 05:29 AM

The problems with unsaturated fats is more related to cross linking than smoking. As you say, there's lots of high volatility stuff in unrefined oils. Generally any compound associated with flavor or aroma is more prone to smoke than the oil, and these would be stripped out in refining.

Medium avatar

(10611)

on July 03, 2012
at 05:28 AM

The problems with unsaturated fates is more related to cross linking than smoking. As you say, there's lots of high volatility stuff in unrefined oils. Generally any compound associated with flavor or aroma is more prone to smoke than the oil, and these would be stripped out in refining.

11
510bdda8988ed0d4b0ec0b738b4edb73

(20898)

on July 01, 2012
at 02:49 AM

Smoke point and oxidation are unrelated. They easily oxidize, and that's because of the double bonds that are easy to radicalize to make room for the oxygen. Smoking has more to deal with their physical properties, they pack together better and are less likely to smoke.

That still doesn't make them safe to cook with because they've oxidized long before smoking. So just stick with saturated fats when you're cooking with any reasonably high temperature. Saturated fats are nearly impossible to oxidize.


edits to answer comments below:

I'm not sure what determines the smoke point. However, I think that most oils would be all free fatty acids, that's what processing and making the oil would do. It would break it out of the triglyceride. Not sure though, it's not something I've ever read about.

Regarding the ease of oxidation: chemistry doesn't happen at "thresholds". That is, there is no magic temperature at which everything oxidizes, above that temperature it's all oxidized and below that temperature nothing is oxidized. It doesn't work that way. All reactions have "rates" or "how fast they occur". Some reactions happen slowly (metal rusting), some happen fast (an explosion is just a really really fast reaction). Generally, reactions will speed up with temperature, and it's not linear. As a rule-of-thumb, you can say that every 10 degrees you raise the temperature, the reaction doubles in speed. That's why you cook food the heat speeds up the cooking reactions. Back to fats and oils: The rate at which they oxidize is determined by how many double bonds there are. The more double bonds, the more quickly they oxidize. So when you heat an easily oxidized fat, it oxidizes even faster. But you could take a slowly oxidizing fat and heat the hell out of it and make it oxidize fast too. It's all about rates, not thresholds. I'm sure there are tons of tables out there listing the temperature-dependent reaction rates of oxidation for a bunch of fats, I just don't know where to look.

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on July 03, 2012
at 01:52 AM

other factors, but am I misunderstanding?

32f5749fa6cf7adbeb0b0b031ba82b46

(41757)

on July 01, 2012
at 06:53 PM

I don't think oil processing intentionally liberates free fatty acids.

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on July 01, 2012
at 11:27 AM

So are there oxidation points (temps) for each type of oil? Do you know of a resource that lists them? Even tallow has some PUFA and MFA, right? So that portion of the fat would be oxidized when cooking?

A2c38be4c54c91a15071f82f14cac0b3

(12682)

on July 01, 2012
at 03:36 AM

Hey chemistry guy (can I call you that?), I have heard smoke point relates to how many free fatty acids there are relative to triglycerides in the oil, is this sort of correct?

510bdda8988ed0d4b0ec0b738b4edb73

(20898)

on July 01, 2012
at 03:06 PM

Well, we prefer the term chemist, but chemistry guy works too. Anyway, I've answered your questions as a big edit in my original answer above. It was easier that way then adding more comments here.

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on July 03, 2012
at 12:56 AM

Thank you, miked. Very helpful.

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on July 03, 2012
at 01:52 AM

I am looking for the kind of table you're describing. I haven't found one yet, but it seems if you take olive oil as an example. If you use refined olive, the smoke point is high, and I've had french fries cooked in refined olive oil. I believe olive oil can oxidize at room temperature over a period of a year or two. Deep frying is at least 200 degree above room temp and (2 years / 2^(200/10)) is a very short time period. That means the olive oil french fries should smell or taste off, right? But they don't. I'm sure the 10 degrees/doubling is a rule of thumb and there are lots of...

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on July 03, 2012
at 01:55 AM

am I misunderstanding? Even lard and tallow have some polyunsatured fats. Wouldn't it be apparent if they were oxidizing during frying?

Ae8946707ddebf0f0bfbcfc63276d823

(9402)

on July 03, 2012
at 01:54 AM

I am looking for the kind of table you're describing. I haven't found one yet, but it seems if you take olive oil as an example. If you use refined olive oil, the smoke point is high, and I've had french fries cooked in refined olive oil. I believe olive oil can oxidize at room temperature over a period of a year or two. Deep frying is at least 200 degree above room temp and (2 years / 2^(200/10)) is a very short time period. That means the olive oil french fries should smell or taste off, right? But they don't. I know you said 10 degrees/doubling is a rule of thumb and not linear, but...

1
4781cf8ae1bfcb558dfb056af17bea94

(4359)

on July 02, 2012
at 07:10 PM

Many have heat-stable antioxidants. Some, like olive oil, do not.

0
Abf0b6d5e20906f742fd600887292c15

on November 25, 2012
at 05:16 PM

So does this mean that smoking point is unrelated to PUFA-content of the fat, and that refining eg. coconut oil and therefore increasing its smoking point wouldn't make it healthier?

I guess lauric acid or whatever the fatty acids in coconut oil would withstand heat very well but that trace minerals and stuff in unrefined coconut oil would make it smoke at a lower temperature? or is something else removed in the refining of the coconut oil

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